This invention relates to folding knives.
In conventional forms of folding knife, the outfolded blade is often shut during use, inflicting a wound on the fingers which are holding the knife.
To eliminate this drawback, various forms of knife are provided. In one form, a leaf spring is assembled in the back of the handle so that the reversal of the outfolded blade is prevented by the elastic force of the leaf spring. In another construction, a spring is mounted inside the handle at its rear end and a lock bar for receiving the elastic force of the spring is pivotably mounted at the back of the handle so that the tang of the outfolded blade is held by one end of the lock bar upon receiving the elastic force of the spring to prevent the reversal of the blade.
In the former construction, however, the range of vertical movement of the leaf spring is rather limited because it is mounted at the back of the knife. Accordingly, the engagement between the blade tang and the tip of the leaf spring becomes smaller, urging easily the blade to the shut position when a force acting in the direction in which the blade is infolded is applied to the back of the blade or the lock bar. If the elasticity of the leaf spring is increased to prevent the above-mentioned drawback, it becomes difficult to release the engagement of the leaf spring with the blade.
In the latter construction, the point where a pressure is applied with respect to the lock bar at the time of releasing the engagement between the blade and the lock bar is a dent provided at the back of the handle in the rear. Furthermore, the direction in which the lock bar is applied with a pressure for disengagement from the blade tang is the same as the direction in which the handle is grasped. When the handle is grasped during use, therefore, the rear portion of the palm often depresses the rear end of the lock bar at the dent, overcoming the elasticity of the leaf spring, causing the lock bar to move whereby the blade is urged to the shut position. This drawback can be eliminated by increasing the elasticity of the leaf spring. If this method is employed, however, disengagement of the lock bar becomes difficult. To increase the depth of the engagement between the blade and the lock bar, the range of vertical movement of the lock bar must be enlarged. However, this range is limited because of the size of the knife. In addition, as a leaf spring is mounted in the back of the handle, the overall size of knife is increased.